Electrical Socket Testing

Dan KeenUpdated February 21, 2017

Electrical sockets, commonly referred to as outlets or receptacles, provide a safe and convenient way to access electricity in buildings. Appliances and electrical devices can quickly and simply be connected and disconnected from the power source by inserting plugs into sockets designed to accommodate them. When there appears to be no power present at an electric socket, first check the building’s circuit breakers or fuse box for tripped breakers or blown fuses. Check other appliances in the building to be sure they are working and that the problem isn’t a power outage or a service disruption to the building's electricity supply.

Test for a Loose Socket

A small lamp is a simple tool for testing standard duplex sockets. Plug the lamp into another socket in the building to ensure the lamp and bulb are working. Plug the lamp into the suspected faulty socket. Feel that the plug is making a secure, tight fit and is not loose. Gently wiggle the electric cord on the lamp where it is attached to the socket. If the lamp light flickers as you wiggle the cord, the socket’s contacts have become worn and are spread apart, failing to make a secure mechanical and electrical connection. This can pose a hazard because sparks can occur from connectors that are making and breaking contact. Do not use the socket again until it is replaced.

Test Adjacent Sockets for Power

Using your test lamp, determine that no power is available from the socket, even when the cord is wiggled. Systematically plug the lamp into each socket in the room. Several sockets that are in the same room are usually wired in parallel--that is, the electric supply wire is routed along a wall and sockets are connected to it. If the lamp lights in all the other sockets, the problem is either the suspected faulty socket or the wire leading to it.

Test for Power Reaching the Socket

Check that power is getting to the socket by turning off the circuit breaker that feeds the outlet. Unscrew the wall plate and remove it. Unscrew the two screws, one at the top and one at the bottom, that mount the socket to the outlet box. Pull the socket out of the box about an inch or two, just far enough to expose the terminal screws on either side of the socket. Turn the circuit breaker back on, but be aware that you are now working on a “live” exposed circuit. You will see two brass terminal screws on one side of the socket and two silver screws on the other side. With a volt meter, place one probe on one of the brass screws and the other probe on one of the silver screws. If the meter indicates voltage is present, the socket is faulty. Otherwise, there is either a break in the wire that feeds the socket, or more likely, the wire has become disconnected at an adjacent socket where it is tied in. Pull out the sockets on both sides of the problem socket and check the wiring.

Test GFCI Sockets

A ground-fault circuit interrupter, or GFCI, is a special type of electrical socket that provides additional safety from shocks by including a circuit breaker within the socket housing. They are typically used where water is present, such as in kitchens and bathrooms, and in outside weatherproof boxes. These sockets have a “test” and “reset” button right on the front of the socket face. Plug your test lamp into the GFCI and press the “reset” button. If that fails to solve the problem, follow the procedure in the previous paragraph to test for voltage at the GFCI’s screw terminals.

Different Socket Configurations

Electric utility companies around the world have varying standards for the voltage and frequency of the power they deliver. Electric sockets also differ in size and shape in foreign countries. Even within the same country, there can be regional differences. Testing these sockets is similar to the procedure described in previous sections. When travelling, adaptors are available to convert appliance plugs to foreign sockets, as may be needed to use an electric shaver.

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About the Author

Dan Keen is the publisher and editor of a county newspaper in New Jersey. For over 30 years he has written books and magazine articles for such publishers as McGraw-Hill. Keen holds a degree in electronics, was chief engineer for two radio stations and taught computer science at Stockton State College.